Inductor structure with magnetic material and method for forming the same

ABSTRACT

Embodiments of mechanisms of forming an inductor structure are provided. The inductor structure includes a substrate and a first dielectric layer formed over the substrate. The inductor structure includes a first metal layer formed in the first dielectric layer and a second dielectric layer over the first metal layer. The inductor structure further includes a magnetic layer formed over the first dielectric layer, and the magnetic layer has a top surface, a bottom surface and sidewall surfaces between the top surface and the bottom surface, and the sidewall surfaces have at least two intersection points.

BACKGROUND

Semiconductor devices are used in a variety of electronic applications,such as personal computers, cell phones, digital cameras, and otherelectronic equipment. Semiconductor devices are typically fabricated bysequentially depositing insulating or dielectric layers, conductivelayers, and semiconductive layers of material over a semiconductorsubstrate, and patterning the various material layers using lithographyto form circuit components and elements thereon.

Generally, an inductor is a passive electrical component that can storeenergy in a magnetic field created by an electric current passingthrough it. An inductor may be constructed as a coil of conductivematerial wrapped around a core of dielectric material. One parameter ofan inductor that may be measured is the inductor's ability to storemagnetic energy, also known as the inductor's inductance. Anotherparameter that may be measured is the inductor's Quality (Q) factor. TheQ factor of an inductor is a measure of the inductor's efficiency andmay be calculated as the ratio of the inductor's inductive reactance tothe inductor's resistance at a given frequency.

Inductors may be utilized in a wide variety of applications. One suchapplication of an inductor may be as a choke, in which an inductor isdesigned to have a high inductive reactance to, or block, signals withcertain frequencies in an electrical circuit while allowing passage ofother signals at different frequencies in the electrical circuit. Achoke may be made, for example to block a radio frequency (RF), and maybe called a RF choke, which is of use in radio communications.

However, there are many challenges for forming the inductor.

BRIEF DESCRIPTION OF THE DRAWING

For a more complete understanding of the present disclosure, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIGS. 1A-1C show cross-sectional representations of various stages offorming an inductor structure, in accordance with some embodiments ofthe disclosure.

FIGS. 2A-2H shows cross-sectional representation of various stages offorming an inductor structure, in accordance with some embodiments ofthe disclosure.

FIG. 3A shows a top-view of an inductor structure, in accordance withsome embodiments of the disclosure.

FIG. 3B shows a cross-sectional representation of an inductor structurealong BB′ in FIG. 3A, in accordance with some embodiments of thedisclosure.

FIG. 3C shows a cross-sectional representation of an inductor structurealong CB′ in FIG. 3A, in accordance with some embodiments of thedisclosure.

DETAILED DESCRIPTION

The making and using of the embodiments of the disclosure are discussedin detail below. It should be appreciated, however, that the embodimentscan be embodied in a wide variety of specific contexts. The specificembodiments discussed are merely illustrative, and do not limit thescope of the disclosure.

It is to be understood that the following disclosure provides manydifferent embodiments, or examples, for implementing different featuresof the disclosure. Specific examples of components and arrangements aredescribed below to simplify the present disclosure. These are, ofcourse, merely examples and are not intended to be limiting. Moreover,the performance of a first process before a second process in thedescription that follows may include embodiments in which the secondprocess is performed immediately after the first process, and may alsoinclude embodiments in which additional processes may be performedbetween the first and second processes. Various features may bearbitrarily drawn in different scales for the sake of simplicity andclarity. Furthermore, the formation of a first feature over or on asecond feature in the description may include embodiments in which thefirst and second features are formed in direct or indirect contact.

Some variations of the embodiments are described. Throughout the variousviews and illustrative embodiments, like reference numbers are used todesignate like elements.

Embodiments of mechanisms for forming an inductor structure 100 areprovided. FIGS. 1A-1C show cross-sectional representations of variousstages of forming an inductor structure 100 in accordance with someembodiments of the disclosure. However, it should be noted that FIGS. 1Ato 1C have been simplified for the sake of clarity to better understandthe inventive concepts of the disclosure. Additional features can beadded in inductor structure 100, and some of the features below can bereplaced or eliminated.

Referring to FIG. 1A, a semiconductor substrate 102 is provided.Semiconductor substrate 102 may be made of silicon or othersemiconductor materials. Alternatively or additionally, semiconductorsubstrate 102 may include other elementary semiconductor materials suchas germanium. In some embodiments, semiconductor substrate 102 is madeof a compound semiconductor such as silicon carbide, gallium arsenic,indium arsenide, or indium phosphide. In some embodiments, semiconductorsubstrate 102 is made of an alloy semiconductor such as silicongermanium, silicon germanium carbide, gallium arsenic phosphide, orgallium indium phosphide. In some embodiments, semiconductor substrate102 includes an epitaxial layer. For example, semiconductor substrate102 has an epitaxial layer overlying a bulk semiconductor.

Semiconductor substrate 102 may further include isolation features (notshown), such as shallow trench isolation (STI) features or localoxidation of silicon (LOCOS) features. The isolation features may defineand isolate various integrated circuit devices. Integrated circuitdevices, such as metal oxide semiconductor field effect transistors(MOSFET), complementary metal oxide semiconductor (CMOS) transistors,bipolar junction transistors (BJT), high voltage transistors, highfrequency transistors, p-channel and/or n-channel field effecttransistors (PFETs/NFETs), etc.), diodes, or other suitable elements,are formed in and/or on semiconductor substrate 102.

Semiconductor substrate 102 may also include various p-type dopedregions and/or n-type doped regions, implemented by a process such asion implantation and/or diffusion. Those doped regions include n-well,p-well, light doped region (LDD), heavily doped source and drain (S/D),and various channel doping profiles configured to form variousintegrated circuit (IC) devices, such as resistors, capacitors,inductors, diodes, metal-oxide-semiconductor field effect transistors(MOSFETs), complementary MOS (CMOS) transistors, bipolar junctiontransistors (BJTs), laterally diffused MOS (LDMOS) transistors, highpower MOS transistors, fin-like field effect transistors (FinFETs),imaging sensor, light emitting diode (LED), or other applicablecomponents.

Semiconductor substrate 102 may also include gate stacks formed bydielectric layers and electrode layers. The dielectric layers mayinclude an interfacial layer (IL) and a high-k (HK) dielectric layer.The dielectric layers are deposited by suitable techniques, such aschemical vapor deposition (CVD), atomic layer deposition (ALD), physicalvapor deposition (PVD), thermal oxidation, or other applicabletechniques. The electrode layers may include a single layer or multiplelayers, such as metal layer, liner layer, wetting layer, and adhesionlayer, formed by ALD, PVD, CVD, or other applicable process.

As shown in FIG. 1A, an interconnect structure 110 is formed oversemiconductor substrate 102. In some embodiments, interconnect structure110 is embedded in inter-metal dielectric (IMD) layers 114. Interconnectstructure 110 is configured to couple the various p-type and n-typedoped regions and the other functional features (such as gateelectrodes), resulting a functional integrated circuit. Interconnectstructure 110 includes first metal layer 112, contacts (not shown) andvia features (not shown). In some embodiments, first metal layer 112 isthe topmost metal layer and called as M_(top). First metal layer 112provides horizontal electrical routing. The contacts provide verticalconnection between silicon substrate and metal lines while via featuresprovide vertical connection between metal lines in different metallayers. In some embodiments, inter-metal dielectric (IMD) layers 114 ismade by silicon oxide, silicon nitride, silicon oxy-nitride, siliconcarbide, BSG, BPSG, low-k or ultra low-k dielectrics.

In some embodiments, interconnect structure 110 is formed in aback-end-of-line (BEOL) process. First metal layer 112 may be made ofconductive material, such as copper (Cu), copper alloy, aluminum (Al),aluminum alloy, tungsten (W), tungsten alloy, or applicable materials.In some embodiments, first metal layer 112 is copper or copper alloy. Insome embodiments, first metal layer 112 is formed by single and/or dualdamascence processes.

As shown in FIG. 1A, an etching stop layer 120 is formed overinterconnect structure 110. In some embodiments, etching stop layer 120is made of silicon nitride.

After forming etching stop layer 120 over interconnect structure 110, amagnetic layer 130 is formed over etching stop layer 120. Magnetic layer130 is insulated from metal lines 112 by etching stop layer 120.Magnetic layer 130 includes cobalt (Co), zirconium (Zr), tantalum (Ta)and niobium (Nb), rhenium (Re), neodymium (Nd), praseodymium (Pr), ordysprosium (Dy).

In some embodiments, magnetic layer 130 includes an amorphous cobalt(Co) alloy including cobalt (Co) and zirconium (Zr). Zirconium (Zr)helps make cobalt (Co) amorphous. In some embodiments, magnetic layer130 includes a cobalt-zirconium (CoZr) alloy having one or moreadditional elements, such as tantalum (Ta) and niobium (Nb). In someother embodiments, magnetic layer 130 includes a cobalt-zirconium (CoZr)alloy having one or more additional elements, such as a rare earthelement, that help increase the ferromagnetic resonance of thecobalt-zirconium (CoZr) alloy. Rare earth elements include rhenium (Re),neodymium (Nd), praseodymium (Pr), or dysprosium (Dy).

Afterwards, a photoresist layer 150 is formed over magnetic layer 130.Photoresist layer 150 is patterned by a photolithography process to forma pattered photoresist layer 150. In some embodiments, photoresist layer150 is a positive photoresist and includes a polymer which isphoto-solubilized when exposed to light. In some embodiments,photoresist layer 150 is formed by a spin-on coating method.

After forming patterned photoresist layer 150 over magnetic layer 130,an etching process 11 is performed on magnetic layer 130 as shown inFIG. 1B in accordance with some embodiments of the disclosure. Etchingprocess 11 is used to remove a portion of magnetic layer 130. In someembodiments, an etching solution used in etching process 11 includes HF,HNO₃ and water. In some embodiments, etching process 11 is operated at atemperature in a range from about 15° C. to about 40° C.

However, as shown in FIG. 1B, a lateral etching rate of etching process11 in X-direction is larger than a vertical etching rate of etchingprocess 11 in Y-direction. Therefore, a lateral portion of magneticlayer 130 is etched heavily than a vertical portion of magnetic layer130. As a result, a volume of magnetic layer 130 is largely decreased byetching process 11.

Afterwards, a second inter-metal dielectric (IMD) layer 140 is formedover magnetic layer 130 and etching stop layer 120 as shown in FIG. 1Cin accordance with some embodiments of disclosure. Trenches are formedin second IMD layer 140 by a photolithography process and an etchingprocess. Conductive materials are filling into the trenches to form vias160 and second metal layer 162. In some embodiments, a spiral structureis made by first metal layer 112, the vias 160 and second metal layer162.

Vias 160 are formed in second IMD layer 140, and a second metal layer162 is formed over vias 160 and second IMD layer 140. Vias 160 andSecond metal layer 162 independently may be made of conductive material,such as copper (Cu), copper alloy, aluminum (Al), aluminum alloy,tungsten (W), tungsten alloy, or applicable materials. In someembodiments, inductor structure 100 is made by magnetic layer 130, firstmetal layer 112, the vias 160 and second metal layer 162.

As mentioned above, the lateral etching rate of etching process 11 inX-direction is larger than the vertical etching rate of etching process11 in Y-direction. Therefore, the volume of magnetic layer 130 islargely decreased by etching process 11. Furthermore, the performance ofinductor structure 100 is decreased by the small volume of magneticlayer 130. For example, a Q factor of inductor structure 100 isdecreased due to small volume of magnetic layer 130. In order to improveperformance of inductor structure 100, a large volume of magnetic layer130 is needed.

FIGS. 2A-2H show cross-sectional representations of various stages offorming inductor structure 100 in accordance with some embodiments ofthe disclosure. Referring to FIG. 2A, an oxide layer 124 is deposited onetch stop layer 120. In some embodiments, oxide layer 124 is made ofsilicon oxide, silicon nitride, silicon oxy-nitride, silicon carbide,borosilicate glass (BSG), borophosphosilicate glass (BPSG). Afterforming oxide layer 124, photoresist layer 150 is formed over oxidelayer 124. Afterwards, photoresist layer 150 is patterned by aphotolithography process to form a pattered photoresist layer 150.

After forming pattered photoresist layer 150, oxide layer 124 ispatterned by using pattered photoresist layer 150 as a mask to form apatterned oxide layer 124 as shown in FIG. 2B in accordance with someembodiments of disclosure. In some embodiments, the material of oxidelayer 124 is the same as that of inter-metal dielectric (IMD) layers114. In some embodiments, oxide layer 124 has a height in a range fromabout 0.5 μm to about 20 μm. As shown in FIG. 2B, an opening 125 isformed in oxide layer 124.

After oxide layer 124 is patterned, magnetic layer 130 is conformallyformed on oxide layer 124 to fill into opening 125 as shown in FIG. 2Cin accordance with some embodiments of disclosure. Magnetic layer 130 isdisposed in the central portion (or core) of inductor structure 100 (asshown in FIG. 3A) to increase the inductance of inductor structure 100.

Magnetic layer 130 has two portions including first portion 131 overetch stop layer and a second portion 132 over oxide layer 124. Firstportion further includes a horizontal portion 131 h and a verticalportion 131 v, and the vertical portion 131 v lines with sidewall ofopening 125. The horizontal portion 131 h of first portion 131 ofmagnetic layer 130 has a height H₂. In some embodiments, height H₁ ofoxide layer 124 is larger than or equal to height H₂ of horizontalportion 131 h. In some embodiments, a ratio (H₁/H₂) of height H₁ toheight H₂ is in a range from about 0.2 to about 5.

After magnetic layer 130 is formed over etch stop layer 120 and oxidelayer 124, a second photoresist layer 150′ is conformally formed overthe first portion of magnetic layer 130 as shown in FIG. 2D inaccordance with some embodiments of disclosure. In some embodiments, amask used to form patterned photoresist layer 150 in FIG. 2A has a cleartone, and the same mask used to form second patterned photoresist layer150′ in FIG. 2D has a dark tone. Thus, patterned photoresist layer 150and second patterned photoresist layer 150′ are formed by using the samemask without two masks.

After second patterned photoresist layer 150′ are formed over magneticlayer 130, etching process 11 is performed on magnetic layer 130 asshown in FIG. 2E in accordance with some embodiments of disclosure.Etching process 11 is used to remove a portion of magnetic layer 130. Insome embodiments, an etching solution used in etching process 11includes HF in a range from about 3% to about 15%, HNO₃ in a range fromabout 10% to about 50%, and water in a range from about 30% to about90%. In some embodiments, etching process 11 is operated at atemperature in a range from about 15° C. to about 40° C.

As mentioned above, the lateral etching rate of etching process 11 inX-direction is larger than the vertical etching rate of etching process11 in Y-direction. It should be noted that because oxide layer 124 isformed below magnetic layer 130 to raise a portion of magnetic layer130. A top surface of second portion 132 of magnetic layer 130 is higherthan a top surface of first portion 131 of magnetic layer 130. Sincelateral etching rate of etching process 11 is larger than verticaletching rate, as mentioned above, second portion 132 of magnetic layer130 is etched firstly, and vertical portion 131 v of first portion 131of magnetic layer 130 is etched afterwards. Therefore, horizontalportion 131 h of first portion of magnetic layer 130 is slightly etchingdue to the protection of oxide layer 124.

It should be noted that oxide layer 124 provides a base to raise aportion of magnetic layer 130. Additionally, oxide layer 124 is as aprotection layer to prevent magnetic layer 130 from over etching.Therefore, the volume of magnetic layer 130 is not decreased largely byetching process 11.

After etching process 11, magnetic layer 130 has polygon structure asshown in FIG. 2F in accordance with some embodiments of disclosure. Asshown in FIG. 2F, Magnetic layer 130 has an octagon structure. Magneticlayer 130 has a top surface 130T, a first sidewall surface 130 a, asecond sidewall surface 130 b, a third sidewall surface 130 c, a bottomsurface 130B, a fourth sidewall surface 130 d, a fifth sidewall surface130 e and a sixth sidewall surface 130 f. Top surface 130T is a topplanar surface, and bottom surface 130B is a bottom planar surface. Topsurface 130T is parallel to bottom surface 130B.

Magnetic layer 130 has right sidewall surfaces and left sidewallsurfaces which are disposed oppositely to each other. Right sidewallsurfaces include first sidewall surface 130 a, second sidewall surface130 b and third sidewall surface 130 c. Left sidewall surfaces includefirst sidewall surface 130 a, second sidewall surface 130 b and thirdsidewall surface 130 c. The right sidewall surfaces of magnetic layer130 have three intersection points. An first intersection point P₁ isformed between top surface 130T and first sidewall surface 130 a, and ansecond intersection point P₂ is formed between first sidewall surface130 a and second sidewall surface 130 b, and a third intersection pointP₃ is formed between second sidewall surface 130 b and third sidewallsurface 130 c. Similarly, the left sidewall surfaces of magnetic layer130 have at least two intersection points including fourth intersectionpoint P₄, fifth intersection point P₅ and sixth intersection point P₆.

In some embodiments, an angle α₁ between first sidewall surface 130 aand second sidewall surface 130 b is in a range from about 30 degrees toabout 85 degrees. In some embodiments, an angle α₂ between secondsurface 130 b and third surface 130 c is in a range from about 95degrees to about 150 degrees.

In some other embodiments, magnetic layer 130′ has a trapezoid structureas shown in FIG. 2F′ in accordance with some embodiments of disclosure.Magnetic layer 130′ has a top surface 130′T, a first sidewall surface130 a, a second sidewall surface 130′b, a bottom surface 130′B, a thirdsidewall surface 130 c and a fourth sidewall surface 130′d. Top surface130′T is a top planar surface, and bottom surface 130′B is a bottomplanar surface. Top surface 130′T is parallel to bottom surface 130′B.

The right sidewall surfaces of magnetic layer 130′ have two intersectionpoints. An first intersection point P₁′ is formed between top surface130′T and first sidewall surface 130′a, and an second intersection pointP₂′ is formed between first sidewall surface 130′a and second sidewallsurface 130′b. Similarly, the left sidewall surfaces of magnetic layer130′ have at least two intersection points including third intersectionpoint P₃′, fourth intersection point P₄′.

In some embodiments, an angle β₁ between first sidewall surface 130′aand second sidewall surface 130′b is in a range from about 120 degreesto about 175 degrees. In some embodiments, an angle β₂ between secondsurface 130′b and third surface 130′c is in a range from about 95degrees to about 150 degrees.

After magnetic layer 130 is etched by etching process 11, secondinter-metal dielectric (IMD) layer 140 is formed over oxide layer 124and magnetic layer 130 as shown in FIG. 2G in accordance with someembodiments of disclosure.

Afterwards, as shown in FIG. 2H, trenches are formed in second IMD layer140 by a photolithography process and an etching process. Conductivematerials are filling into the trenches to form vias 160 and secondmetal layer 162. Second metal layer 162 is electrically connected tofirst metal layer 112 through vias 160. Inductor structure 100 isconstructed by first metal layer 114, second metal layer 162 andmagnetic layer 130.

It should be noted that a portion of magnetic layer 130 is formed onoxide layer 124 (as shown in FIG. 2D). Therefore, the vertical portionof magnetic layer 130 lining with sidewall of opening 125 is etchingfirstly by etching process 11 (as shown etching direction marked as anarrow 11 a). Compared with magnetic layer 130 shown in FIG. 1C, magneticlayer 130 shown in FIG. 2F and 2F′has a larger volume. As a result,performance of inductor structure 100 including large volume of magneticlayer 130 has a better performance (high Q factor).

FIG. 3A shows a top-view of inductor structure 100, in accordance withsome embodiments of the disclosure. A spiral structure is made by firstmetal layer 112, the vias 160 and second metal layer 162. Magnetic layer130 formed by processes of FIG. 2A-2H is disposed in a central portionof inductor structure 100 and surrounded by the spiral structure.Magnetic layer 130 has the polygon structure, such as octagon ortrapezoid structure with a large volume to increase the Q factor ofinductor structure 100.

FIG. 3B shows a cross-sectional representation of an inductor structure100 along BB′ in FIG. 3A in accordance with some embodiments of thedisclosure. First metal layer 114 is electrically connected to secondmetal layer 162 through vias 160, and second metal layer 162 iselectrically connected to a third metal layer (not shown) through asecond via 164.

FIG. 3C shows a cross-sectional representation of an inductor structure100 along CB′ in FIG. 3A in accordance with some embodiments of thedisclosure. Magnetic layer 130 has the octagon structure with the largevolume to increase the Q factor of inductor structure 100.

Embodiments of mechanisms of forming an inductor structure are provided.A magnetic layer is disposed in the central portion (or core) of aninductor structure to increase the inductance of the inductor structure.An oxide layer is formed below a portion of the magnetic layer toprevent the magnetic layer from over etching. Therefore, a large volumeof inductor structure is obtained. The performance of the inductorstructure is improved by increasing the volume of inductor structure. Inaddition, he Q factor of inductor structure is further improved.

In some embodiments, an inductor structure is provided. The inductorstructure includes a substrate and a first dielectric layer formed overthe substrate. The inductor structure includes a first metal layerformed in the first dielectric layer and a second dielectric layer overthe first metal layer. The inductor structure further includes amagnetic layer formed over the first dielectric layer, and the magneticlayer has a top surface, a bottom surface and sidewall surfaces betweenthe top surface and the bottom surface, and the sidewall surfaces haveat least two intersection points.

In some embodiments, an inductor structure is provided. The inductorstructure includes a substrate and a first metal layer formed in a firstdielectric layer. The inductor structure includes a magnetic layerformed on the first dielectric layer, and the magnetic layer has anoctagon or trapezoid structure. The inductor structure also includes anoxide layer formed adjacent to magnetic layer. The inductor structurefurther includes a second dielectric layer formed over the magneticlayer and the oxide layer and a second metal layer formed on a seconddielectric layer.

In some embodiments, a method for forming an inductor structure isprovided. The method includes providing a substrate and forming a firstmetal layer in a first dielectric layer. The method also includesforming and patterning a oxide layer to form an opening in the oxidelayer, and conformally forming a magnetic material on the oxide layerand in the opening. The method also includes forming a photoresist layerover the magnetic material, and performing a wet etching process on themagnetic material to form a magnetic layer. The method further includesforming a second dielectric layer on the magnetic layer and forming asecond metal layer on the second dielectric layer.

Although embodiments of the present disclosure and their advantages havebeen described in detail, it should be understood that various changes,substitutions and alterations can be made herein without departing fromthe spirit and scope of the disclosure as defined by the appendedclaims. For example, it will be readily understood by those skilled inthe art that many of the features, functions, processes, and materialsdescribed herein may be varied while remaining within the scope of thepresent disclosure. Moreover, the scope of the present application isnot intended to be limited to the particular embodiments of the process,machine, manufacture, composition of matter, means, methods and stepsdescribed in the specification. As one of ordinary skill in the art willreadily appreciate from the disclosure of the present disclosure,processes, machines, manufacture, compositions of matter, means,methods, or steps, presently existing or later to be developed, thatperform substantially the same function or achieve substantially thesame result as the corresponding embodiments described herein may beutilized according to the present disclosure. Accordingly, the appendedclaims are intended to include within their scope such processes,machines, manufacture, compositions of matter, means, methods, or steps.

1. An inductor structure, comprising: a substrate; a first dielectriclayer formed over the substrate; a first metal layer formed in the firstdielectric layer; a second dielectric layer over the first metal layer;a magnetic layer formed over the first dielectric layer, wherein themagnetic layer has a top surface, a bottom surface and sidewall surfacesbetween the top surface and the bottom surface, and the sidewallsurfaces have at least two intersection points, and wherein the sidewallsurfaces comprise a first pair of sidewall surfaces adjoin the bottomsurface and a second pair of sidewall surfaces adjoin the first pair ofsidewall surfaces, wherein the first pair of sidewall surfaces arevertical to the bottom surface of the magnetic layer; and the secondpair of sidewall surfaces taper gradually toward the top surface of themagnetic layer.
 2. The inductor structure as claimed in claim 1, whereinthe sidewall surfaces comprises a first sidewall surface, a secondsidewall surface and a third sidewall surface, the first sidewallsurface is connected to top surface, and an angle between the firstsidewall surface and the second sidewall surface is in a range about 30degrees to about 85 degrees.
 3. The inductor structure as claimed inclaim 3, wherein the third sidewall surface is connected to the bottomsurface, and an angle between the second sidewall surface and the thirdsidewall surface is in a range about 95 degrees to about 150 degrees. 4.The inductor structure as claimed in claim 1, wherein the sidewallsurfaces comprises a first sidewall surface and a second sidewallsurface, the first sidewall surface is connected to top surface, and anangle between the top surface and the first sidewall surface is in arange about 120 degrees to about 175 degrees.
 5. The inductor structureas claimed in claim 4, wherein an angle between the first sidewallsurface and the second sidewall surface is in a range about 95 degreesto about 150 degrees.
 6. The inductor structure as claimed in claim 1,wherein the magnetic layer comprises cobalt (Co), zirconium (Zr),tantalum (Ta) and niobium (Nb), rhenium (Re), neodymium (Nd),praseodymium (Pr), or dysprosium (Dy) or combinations thereof.
 7. Theinductor structure as claimed in claim 1, wherein a spiral structure ismade by the first metal layer, vias and a second metal layer.
 8. Theinductor structure as claimed in claim 7, wherein the magnetic layer issurrounded by the spiral structure.
 9. The inductor structure as claimedin claim 1, further comprising: an etch stop layer formed on the firstmetal layer, wherein the magnetic layer is insulated from the firstmetal layer by the etch stop layer.
 10. The inductor structure asclaimed in claim 1, further comprising: vias formed in the seconddielectric layer; and a second metal layer formed on the vias, whereinthe second metal layer is electrically connected to the first metallayer by the vias.
 11. The inductor structure as claimed in claim 1,wherein the magnetic layer has a polygon structure.
 12. An inductorstructure, comprising: a substrate; a first metal layer formed in afirst dielectric layer; a magnetic layer formed on the first dielectriclayer, wherein the magnetic layer has an octagon or trapezoid structure,and wherein the magnetic layer has sidewall surfaces which comprise afirst pair of sidewall surfaces adjoin the bottom surface and a secondpair of sidewall surfaces adjoin the first pair of sidewall surfaces,wherein the first pair of sidewall surfaces are vertical to the bottomsurface of the magnetic layer; and the second pair of sidewall surfacestaper gradually toward the top surface of the magnetic layer; an oxidelayer formed adjacent to magnetic layer; a second dielectric layerformed over the magnetic layer and the oxide layer; and a second metallayer formed on a second dielectric layer.
 13. The inductor structure asclaimed in claim 12, further comprising: an etch stop layer formed onthe first metal layer, wherein the first metal layer is insulated fromthe magnetic layer by an etch stop layer.
 14. The inductor structure asclaimed in claim 12, wherein the magnetic layer has a top surface, abottom surface and sidewall surfaces between the top surface and thebottom surface, and the sidewall surfaces have at least two intersectionpoints.
 15. The inductor structure as claimed in claim 12, furthercomprising: vias formed in the second dielectric layer and the oxidelayer, wherein the first metal layer is electrically connected to thesecond metal layer through the vias.
 16. A method for forming theinductor structure of claim 1, comprising: providing a substrate;forming a first metal layer in a first dielectric layer; forming andpatterning a oxide layer to form an opening in the oxide layer;conformally forming a magnetic material on the oxide layer and in theopening; forming a photoresist layer over the magnetic material;performing a wet etching process on the magnetic material to form amagnetic layer; after performing the wet etching process, the magneticlayer comprising sidewall surfaces which comprise a first pair ofsidewall surfaces adjoin the bottom surface and a second pair ofsidewall surfaces adjoin the first pair of sidewall surfaces, whereinthe first pair of sidewall surfaces are vertical to the bottom surfaceof the magnetic layer; and the second pair of sidewall surfaces tapergradually toward the top surface of the magnetic layer; forming a seconddielectric layer on the magnetic layer; and forming a second metal layeron the second dielectric layer.
 17. The method for forming an inductorstructure as claimed in claim 16, wherein performing the wet etchingprocess comprises using a wet etching solution comprising HF, HNO3 andwater.
 18. The method for forming an inductor structure as claimed inclaim 16, before forming and patterning the oxide layer, furthercomprising: forming an etching stop layer on the first dielectric layer.19. The method for forming an inductor structure as claimed in claim 16,wherein a ratio of a height of the oxide layer to a height of themagnetic material is in a range from about 0.2 to about
 5. 20. Themethod for forming an inductor structure as claimed in claim 16, beforeforming the second metal layer on the second dielectric layer, furthercomprising: forming vias in the second dielectric layer and oxide layer.